1. Field of the Invention
This invention relates generally to devices for the electroencephalographic (EEG) acquisition of neurophysiological brain electrical signals, and more particularly concerns a headset which is an electrode positioning device. The headset is used for acquiring high quality EEG signals and is comfortable for prolonged usage.
2. Description of Related Art
Functional neuroimaging techniques promise to advance research on neural bases of cognitive processes. There are significant technical differences among the neuroimaging techniques. There are at least four major advantages in using EEG over metabolic imaging techniques (such as PET or fMRI) to study the functions of the human brain. These are: EEG electric field recording reflects actual nerve cell activity (there is no estimated metabolic delay); the brain processes can be followed from millisecond to millisecond (no averaging over seconds and consequent smearing of data); building an EEG laboratory and maintaining it is inexpensive compared to building and running a metabolic imaging laboratory; and, in EEG, delivering stimuli and communication with a subject during recording are relatively uncomplicated.
Scalp recording of brain electrical activity, as ongoing EEG and stimulus-registered Event-Related Potentials (ERPs), has provided useful insights to cognitive functions through neurophysiologic neuropsychology studies employing computerized quantitative analysis of EEG and ERP signals.
For example, advances in detection and analysis of EEG brain neuroelectric signals have allowed EEG monitoring to be useful in assessing neurological disorders, and in laboratory research studies of attention, memory, cognitive ability and the effects of drugs. Devices for monitoring EEG signals for such assessments and studies are typically used in clinics or laboratories or in a home environment, and are typically set up and operated by trained technicians.
In fitting EEG electrodes to the scalp of a subject being monitored, a technician will typically first measure the distances between the nasion and the occipital bone and between the pre-auricular notches-to, identify the top center (Cz) of the head, and will then position all other electrodes relative to these landmarks to comply with the International 10/20 and Extended 10/10 Systems that is generally accepted as the standard for positioning of EEG electrodes. The technician will then part the hair of the scalp of the human subject at the intended electrode sites, clean the sites to remove dirt and hair oil, and gently abrade the scalp to remove the top layer of dead skin to ensure a good conductive connection (low scalp-electrode impedance values).
A number of hats, caps, helmets and headgear are known that have been suggested or developed to position anywhere from 1 to over 120 EEG electrodes according to the International 10/20 and Extended 10/10 Systems. They provide a scalp-electrode interface, with or without the use of an adhesive. However, many of these devices are commonly cumbersome, uncomfortable, and unacceptable for use during prolonged testing periods.
It is desirable to provide an EEG electrode locator headset that utilizes means to accurately identify electrode sites, and gives the technician easy access for application of electrodes to the electrode sites. It is also desirable to provide an EEG electrode headset utilizing a location mechanism allowing a technician to prepare an intended electrode site on the scalp prior to seating and placement of the electrodes.